Air investigators are to examine a second black box which was recovered from flight MH17 today.
The data could reveal if the pilots were aware of a missile coming towards the plane and what happened in the last few seconds of the flight if they were able to speak.
Russia probably has "really valuable information" on the MH17 plane crash, which left 298 people dead, and should "release what they know", David Cameron said.
The Prime Minister, who was speaking during a visit to the Shetland Islands, also welcomed the "good news" of fresh sanctions being imposed on Russia by the European Union.
He said: "I would make the point that the people who probably have the really valuable information about what happened to this flight are the Russians and they should release what they know about what happened over the skies of eastern Ukraine."
Thousands of online users have taken to social media to call for the victims of the Malaysian airliner crash to be returned to loved ones.
United States intelligence officials admitted that they do not know who fired the surface-to-air missile that downed flight MH17.
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